Interactive input systems that allow users to inject input (e.g. digital ink, mouse events etc.) into an application program using an active pointer (e.g., a pointer that emits light, sound or other signal), a passive pointer (e.g., a finger, cylinder or other suitable object) or other suitable input device such as for example, a mouse or trackball, are known. These interactive input systems include but are not limited to: touch systems comprising touch panels employing analog resistive or machine vision technology to register pointer input such as those disclosed in U.S. Pat. Nos. 5,448,263; 6,141,000; 6,337,681; 6,747,636; 6,803,906; 7,232,986; 7,236,162; and 7,274,356 assigned to SMART Technologies ULC of Calgary, Alberta, Canada, assignee of the subject application, the entire contents of which are incorporated by reference; touch systems comprising touch panels employing electromagnetic, capacitive, acoustic or other technologies to register pointer input; tablet personal computers (PCs); laptop PCs; personal digital assistants (PDAs); and other similar devices.
A number of applications that generate calligraphic ink from a user's handwritten input (i.e. ordinary ink) have been considered. For example, these applications include Microsoft Tablet PC applications, and the calligraphy tool implemented in the Inkscape Open Source vector graphics editor. Compared to ordinary ink, which is represented as a pixel-based image object, calligraphic ink is represented as a vectorized image. As a result, calligraphy ink has a smoother appearance than ordinary ink, and can be arbitrarily zoomed without showing jagged or zig-zag lines (i.e. stair-stepping) that are usually seen at the edges of a zoomed ordinary ink object. Unfortunately existing calligraphic ink generating applications still exhibit disadvantages. In particular, existing calligraphic ink generating applications are slow, do not present the outlines of calligraphic ink objects with the desired degree of smoothness and do not readily permit portions of calligraphic ink objects to be erased.
Methods of erasing ink objects have been considered. For example, U.S. Pat. No. 6,326,954 to Van leperen et al. entitled “Method For Erasing On An Electronic Writeboard”, assigned to SMART Technologies ULC of Calgary, Alberta, Canada, assignee of the subject application, teaches a method of erasing at least a portion of an ink object displayed on an electronic writeboard. However, when this method is applied to calligraphic ink objects, the degree of smoothness of the unerased portion of the calligraphic ink object typically does not meet the desired standard.
Therefore, there is a need to provide a novel method of generating and erasing calligraphic ink objects on a display surface.